At present, an operation mechanism of a molded case circuit breaker is usually of a manual pick-and-push type, and if a user requires an electric operation, an external electric operation attachment is often provided to be mounted outside the circuit breaker to electrically and remotely control the function of the circuit breaker. However, for a high-capacity molded case circuit breaker, the external operation mechanism attachment tends to have a larger volume and weight, and thus have higher requirements for the mounting quality. In particular, when the operation mechanism cooperates with a circuit breaker body, the substantial impact vibration easily causes failure of key parts such as a circuit breaker housing and a locking device. Therefore, the external operation mechanism attachment of the existing molded case circuit breaker has huge volume, heavy weight and poor reliability. In addition, the previous energy pre-storage operation mechanism is only used on an air circuit breaker, and cannot be applied to the molded case circuit breaker and interchanged with the existing manual pick-and-push type operation mechanism to meet different market needs. Therefore, it is urge to need a novel energy pre-storage operation mechanism built in the circuit breaker to realize intelligent control of the circuit breaker. The operation mechanism has the same mounting way and tripping position as the manual pick-and-push type operation mechanism, realizes the interchange with the manual pick-and-push type operation mechanism, meets the needs of different users, and is capable of overcoming the defects of huge volume, heavy weight, high cost and poor reliability of the manual pick-and-push operation mechanism because the circuit breaker is equipped with an external electric operation attachment.